ESI Audio uniK 05+ and uniK 08+ Active Monitors

A combination of features and sound that’s, well, unique

By Mike Metlay

The German firm ESI Audio is very well known in Europe for everything from interfaces and converters to keyboard controllers and smartphone lavalier mics. Looking through the company’s impressive range of offerings, it might be a little startling to find, at the bottom of the list, studio monitors! What does a company that specializes in digital hardware know about making speakers? Quite a bit, as it turns out.

The ESI speaker line includes a speaker and subwoofer in the 2-way aktiv series, which uses a conventional dome tweeter, and two speakers in the uniK series, which offer flat ribbon tweeters. The uniK speakers have recently been upgraded, the original uniK 05 and unik 08 being replaced by the two “plus” models we’re reviewing here. We had a chance to work with both uniK Plus speakers, and our experience was an ear-opener, to say the least.

So what’s so uniK?

The two models have a lot in common. They’re both 2-way biamplified designs that feature a 49 x 26 mm flat-ribbon magnetostatic tweeter and a woven-Kevlar woofer in a surprisingly classy copper color, built into a rear-ported cabinet with fairly extensive tone controls on the rear panel and some very nice touches in the ‘fit and finish’ department. Both speakers offer a crossover frequency of 3.2 kHz between the two amps, which are matched in output power (40 W each for the uniK 05+ and 70 W each for the uniK 08+).

The cabinet features a rounded front fascia with the two drivers and an ESI logo that glows a coppery orange color when powered on. The rear panel has a single input port that combines balanced XLR and TRS, with a ground lift switch to eliminate ground-loop hum. The standard IEC power cable socket has a power switch and replaceable fuse, and auto- adjusts to global voltage requirements; a Standby switch allows the speaker to automatically power down into idle mode when not used for several minutes (the front logo turns red) and reactivate when it senses audio (with a definite but not overly loud click/pop).

Both speakers come with domed rubberized feet that can be adjusted to different heights thanks to threaded rods and knurled lock washers. Not only does this design provide better isolation than is common with most powered monitors out of the box, but it allows for each speaker to be gently tilted up or down to suit specific monitoring positions.

Trim trim here, tilt tilt there

Rear panel controls are on four small trimpots that require a small flat-head screwdriver (included) to adjust. There’s a Gain trim control (±14 dB), and a pair of shelving EQ controls to tweak lows and highs. The slope of the shelves is pretty gentle, with corner frequencies at roughly 100 Hz and 10 kHz and ±5 dB of adjustment on each. The fourth trimpot is called Character, and it does something I’ve never seen on any other studio monitor: it applies an overall tilt to the entire frequency spectrum from 50 Hz on up. If we assume 0 dB as a reference at 50 Hz, then the Character control can cause the frequency response to rise or fall smoothly by up to ±6 dB at 20 kHz!

These controls offer a lot of leeway, but I would advise using them with a great deal of caution. It’s very tempting to tweak and tweak to get things sounding sweet, but this much control means you have the potential to make your speakers sound quite unrealistic if you’re not careful. In particular, I view the Character control as more of an educational tool than anything one would want to use for reference monitoring, unless it was used in conjunction with tools such as a reference microphone and white noise or sine wave sweeps. ESI notes that Character “allows you to adjust the sound according to the requirements in your room as well as to your own hearing preferences and requirements.” That’s a great thing for casual listening at home, but not something I’d recommend for reference monitoring.

I did play with these controls in my listening space at the Recording offices, and they work smoothly and well, but ultimately in my setup I ended up getting the best and most believable results with all controls left flat. My room’s better treated than many, though, and I could see a Low or High tweak of 1 dB or less benefiting a lot of listening spaces.

Pull out the plug (or not)

Another feature of the uniK speakers, one that’s unusual but not unheard of, is an optional port plug. Whether or not a speaker cabinet is ported is a basic design decision that’s integral to a monitor’s construction; a properly-tuned bass reflex port can do wonders for a smooth frequency response and bass that’s extended without being inaccurate, but proponents of sealed cabinets (with or without passive radiators) believe that porting adds more issues than it solves. I’ve reviewed many monitors with and without porting, and there are great examples of both.

In the case of the uniK models, ESI feels that placement in very tight spaces (as on a bookshelf or in corners of a small room) will result in too much bass emphasis with a rear-ported design, so each speaker is provided with an acoustic-foam bass port plug that fits snugly into the port and seals the cabinet. ESI recommends using the speakers with the ports open when possible, but offers the plug as a practical solution for very tight spaces.

In my listening sessions, I found that the plug mitigated bass boom when the speakers were placed in very cramped locations; for example, I have an office workstation table whose bookshelf is otherwise unusable unless with front-ported speakers. In any other application, removing the ports made the sound really open up and bloom the way it was intended to do. Taking ESI’s advice in this case is a good thing; don’t use the plugs unless you have a bass boom problem that can’t be solved any other way. Judicious use of the Low shelf will almost always be preferable, but hey—it’s nice to have the option, isn’t it?

In use: the uniK 05+

I set up the uniK 05+ in a conventional triangle setup and put it to work on my critical listening library for several days before moving to studio mixing and editing work. I had plenty of time to get over my shock at what these little speakers were providing me.

The uniK 05+ is not a big speaker; it weighs less than 10 pounds and would fit nicely into any studio setup, even very small ones. The big concern with small speakers, of course, is bass extension—how low can you go, and can you trust what you hear? The uniK 05+ claims a frequency response of 49 Hz to 25 kHz with no tolerances given… and based on what I was hearing, I think that number—low as it is— is actually conservative.

Everyone I played music for on the uniK 05+ was frankly stunned at how good the bass was. Whatever ESI is doing with its woofer and porting, it works! This monitor has bass for days, and it’s good bass—tight, clean, detailed, and present, without being woofy or one-note or muddy or overdone. Mids are clean and clear with no hiccups near the crossover frequency, and as expected from a well-made folded ribbon tweeter, the highs are crystal clear with beautiful transients, taking great advantage of the very fast transient response of the amplifiers. Speakers this small have no business sounding this big.

In use: the uniK 08+

After my fantastic experience with the unik 05+, I was reluctant to take them down, but also very curious to hear the unik 08+. It’s a much larger and heavier beastie, weighing just under 20 pounds and pairing an 8″ woofer with the same tweeter and crossover frequency as its sibling. Frequency response is rated (without tolerances) at 37 Hz–25 kHz, which is well into “no, you don’t need a subwoofer unless you’re trying to impress someone” territory.

I initially guessed that the uniK 08+ would basically be the uniK 05+ with more boom, but that wasn’t the whole story. The sweet highs and rich mids were still there, but for want of a better word, the extra 12 Hz on the bottom made the bass response more effortless. At my usual listening SPL of 80 dB at 1 meter, the difference in headroom from the larger amps was pretty obvious, giving the overallimpression that the uniK 08+ was delivering the goods without breathing hard.

Stereo imaging was, if anything, even better than on the uniK 05+, and the sweet spot was comfortably wide for two people sitting side by side, with vocals and lead instruments seeming to float out of the mix with finely etched clarity. Wow, what an experience… after their stint in my studio, I was reluctant to take them down and go back to my usual monitors!

Final thoughts

There’s a lot of competition in this price range, including some really fine monitors that we’ve reviewed in the past. ESI’s uniK Plus speakers stand proudly in that company, and are well worth tracking down for a listen if you can manage it. They have their own character, and it’s one that I happen to trust—the clarity and sweetness of a flat-ribbon tweeter married to the controlled and 3-dimensional power of a properly powered woofer.

The uniK 08+ is a real stalwart in the 8″ 2-way crowd, giving a lot for the money, but if you’re tight on space and worried that a smaller speaker will lie to you about the lowest lows, the uniK 05+ might be the answer to your prayers. Check them out.